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1.
Y型桩桩端阻力产生附加应力的分析计算 总被引：1，自引：0，他引：1
Y型沉管灌注桩截面形式复杂,截面几何特性存在4个独立控制变量、8个积分区间。Y型桩桩端均布荷载在地基内部任意点产生附加应力系数的解析表达式求解困难,目前尚无得出简单的解析表达式。借助数学分析软件Mathematica的NIntegrate数值积分功能,以及Geddes推导应力解的思想,得出了Y型桩桩端均布荷载作用在地基内部任意点竖向附加应力系数的数值计算方法,经校核有很高精度。分析了Y型截面4个独立变量外包圆半径R、模板弧度?、开弧间距s、夹角度数? 对附加应力系数的影响及采用Geddes应力解计算产生的误差。分析了随荷载作用面积变化、计算深度变化Y型、三角形、矩形、方形、圆形、圆环、H形、T形截面桩端均布荷载作用在地基内部时截面中心点下附加应力系数的差异及变化规律。将考虑Y型桩截面形状的附加应力计算方法应用于Y型桩单桩的沉降计算,计算结果与静载荷试验数据吻合较好。 相似文献
2.
This paper presents an analytical method for modeling the dynamic response of a rigid strip footing subjected to vertical-only loads. The footing is assumed to rest on the surface of a viscoelastic half-space; therefore, effects of hysteretic soil damping on the impedance of the foundation and the generated ground vibrations are considered in the solution. To solve the mixed boundary value problem, we use the Fourier transform to cast a pair of dual integral equations providing contact stresses, which are solved by means of Jacobi orthogonal polynomials. The resulting soil and footing displacements and stresses are obtained by means of the Fourier inverse transform. The solution provides more realistic estimates of footing impedance, compared to existing solutions for elastic soil, as well as of the attenuation of ground vibrations with distance of the footing. The latter is important for the estimation of machine vibration effects on nearby structures and installations. 相似文献
3.
移动荷载下黏弹性半空间体上双层板的动力响应 总被引：1，自引：0，他引：1
采用黏弹性半空间体上无限大双层板模型模拟路面结构,通过三重Fourier积分变换得到单位脉冲荷载作用下路面动力响应的Green函数。根据线性系统的叠加原理,利用广义Duhamel积分推导出移动荷载作用下路面动力响应的解析解。采用自适应Simpson法编制了计算奇异、振荡函数的广义积分计算程序,完成了路面动力响应从波数-频率域到时间-空间域的转换。结合算例,对移动荷载作用下路面的振动规律进行研究,讨论上、下层板厚度和板材料的弹性模量对路面动力响应的影响,明确了路面结构的振动特性,研究结果可为路面结构的设计、施工提供理论指导。 相似文献
4.
Tensionless–frictionless interaction of flexible annular foundation with a transversely isotropic multi‐layered half‐space 
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下载免费PDF全文 Morteza Eskandari‐Ghadi Ghasem Gorji‐Bandpey Azizollah Ardeshir‐Behrestaghi Seyed Masoud Nabizadeh 《国际地质力学数值与分析法杂志》2015,39(2):155-174
A transversely isotropic multi‐layered half‐space, with axis of material symmetry perpendicular to the free surface, supports a flexible either annular or solid circle foundation. The contact area of the foundation and the half‐space is considered to be both frictionless and tensionless. The foundation is assumed to be affected by a vertical static axisymmetric load. Detailed analysis of the interaction of these two systems with different thickness of layers is the target of this paper. With the use of ring load Green's functions for both the foundation and the continuum half‐space, an integral equation accompanied with some inequalities is introduced to model the complex BVP. With the incorporation of ring‐shape FEM, we are capable of capturing both regular and singular solution smoothly. The validity of the combination of the analytical and numerical method is proved with comparing the results of this paper with a number of benchmark cases of both linear and nonlinear interaction of circular and annular foundation with half‐space. Some new illustrations are presented to portray the aspect of the anisotropy and layering of the half‐space. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
The dynamic response of a rigid strip footing lying on saturated soil is greatly affected by the pore pressure induced by a rocking moment. To consider the complex behavior of the soil under the rocking load, an analytical solution for a rigid strip foundation on saturated soil under a rocking moment is developed under the framework of Biot’s coupling theory. The boundary-value problem for the governing coupling equations for saturated soil is solved using a Fourier transform to yield a pair of dual integral equations. These dual integral equations are transformed into a set of linear equations using an infinite series of orthogonal Jacobi polynomials to yield the compliance functions. In addition, a parametric study has been carried out to examine the influence of: (1) the dimensionless frequency, (2) the dynamic permeability and (3) the Poisson’s ratio on saturated soil under a rocking rigid strip footing. 相似文献
6.
Tire/ground interaction has been an important issue in terramechanics, transportation and pavement engineering. Characterization of tire/ground interaction has been majorly investigated based on empirical approaches and field tests. So far very few dynamic tire/ground interaction models have been presented. This paper presents a three‐dimensional finite element model for tire/ground interaction. The rubber material is modeled as nearly incompressible finite strain hyperelasticity instead of being modeled as a rigid wheel. The tire is also modeled as bias type and steel rebars are embedded within the tire structure. The tire model is combined with the ground model to form a tire/ground interaction model. Both single tire/ground interaction and four‐tire vehicle/pavement interaction models are presented, which allow us to investigate a lot of issues easily and accurately, such as compaction, pavement response and pavement damage. Numerous simulations are carried out to demonstrate that the dynamic tire/terrain interaction model can be used to predict the dynamic ground response due to moving vehicle. Different tire rolling conditions can be easily incorporated into the tire/ground interaction model, which further substantiates the broad application of the model in transportation and pavement engineering. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
7.
交通荷载作用下公路路基工作区深度研究 总被引：3，自引：0，他引：3
根据路面不平整实测资料,获得了汽车动荷载的计算模型和参数,并利用此荷载模式来分析公路结构的动力响应。考虑到公路结构的三维分层性状,利用Fourier变换技术和求解层状结构的精确刚度矩阵法,研究了公路结构在移动汽车荷载作用下的动力响应问题。为了方便工程应用,利用Odemark厚度和模量的当量转换公式,将公路结构简化为由路面、路基及地基组成的3层体系,并以此为基础分析了路基动应力的衰减规律,同时重点研究了汽车轴载大小、当量路面厚度及路基模量对路基工作区深度的影响,最后建议了路基工作区深度的定量表达式,研究结果可为公路路基设计提供参考。 相似文献
8.
This paper is dedicated to study the dynamic response of a thin‐plate resting on a layered poroelastic half‐space under a moving traffic load. Based on the dynamic poroelastic theory of Biot, the general solutions of the homogeneous poroelastic foundation are obtained by Fourier translation. By using the transmission and reflection matrices method in the frequency domain, the equivalent stiffness of the layered poroelastic half‐space is presented. Kirchhoff's hypotheses are applied to obtain the vertical displacement of the thin plate. By using the inverse Fourier transform, the time domain solution is obtained. As an example of three layers, the influences of the load velocity, the material properties of poroelastic layers, and the flexural rigidity of the plate on the response of the pavement system are examined. Analyses show that a soft intermediate layer results in the significant increase of vertical displacement of road pavement. Comparison with the existing work validates the present model. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
9.
10.
Ardeshir Dehmoobed Sharif-abadi Tim Grain Joseph 《Geotechnical and Geological Engineering》2010,28(4):471-481
Strain softening of oil sand under dynamic loading from large mining equipment inhibits the ability of the equipment to function
at optimal design performance. This paper looks at the findings of dynamic plate load tests, which effectively mimick the
loading and unloading action of a shovel track pad. A pseudo-elastic model was proposed based on the results of the dynamic
plate load testing to predict the deformation of oil sand under cyclic loading. Both field and laboratory cyclic plate load
tests were performed on oil sand materials. The field tests were performed with different plate sizes, or footprints. The
load was normalized based on the pressure stiffness concept in units of pressure per unit deformation. FLAC was used to model
the field plate load test deformation with the elastic concept. The laboratory tests were performed at room temperature with
more control on the load, loading rate, and cycles than possible during the field testing. Tests were conducted using a circular
plate of 14.9 cm diameter, at stress magnitudes of 200, 400, 500 and 600 kPa. The plate load tests were conducted for varying
loads, holding, and relaxation times of 0, 2, 5 and 10 min respectively for each magnitude of stress. The outcome of laboratory
plate load tests show that after frequent cycles, the pressure stiffness (ratio of stress to deformation) converges on a plateau
value of 8 kPa/mm. The proposed approach can be used to evaluate oil sands ground performance, enhancing the prediction process
for ground deformation under the operation of ultra-class mining equipment. 相似文献
11.
工程中多采用基础上拔静载试验中基础顶部荷载-位移曲线获取基础的承载力,忽略了基础周围土体的变形破坏过程,而实际工程中均是基础周围地基土体发生破坏。为研究扩底基础与其周围土体在抗拔承载特性方面的差异,以黄土地基中的9个扩底基础为研究对象,通过现场全尺寸基础的上拔静载试验,分别获得基础顶部与地表的上拔荷载-位移曲线,并进一步对基顶与地表处的荷载-位移曲线变化特征、抗拔承载力取值进行对比分析。结果表明,两处的荷载-位移曲线变化特征相似,相同上拔荷载作用下地表处的位移量均小于基础处位移量,差异以初始弹性阶段变形最为突出;两者在弹性极限荷载QL1取值方面,相差较大,但随着地基基础由弹性向塑性发展,差异逐渐减小,两者塑性极限荷载QL2取值基本相同。结合上拔扩底基础的破坏模式,分析出上述差异主要由于基础与周围土体之间变形不协调所致,加载初期基础顶部的上拔位移包括基础拔出量和上部土体压缩量,当上部土体压密后压缩变形消失,地基基础成为一个整体,上拔基础与周围土体的变形趋于协调。 相似文献
12.
公路交通荷载作用下分层地基的三维动响应分析 总被引：4，自引：1，他引：3
根据高速公路路基的实际情况,建立了三维分层地基模型,分别考虑了刚性路面和柔性路面的情况,利用传递矩阵法获得了置于刚性基岩上的层状地基和分层半无限地基的刚度矩阵,将车辆荷载简化为矩形均布移动荷载,利用Fourier变换方法得到了层状地基系统在交通荷载作用下的三维振动解,并用快速傅立叶逆变换方法得到了数值结果,与模型试验结果进行了比较,显示出了较好的一致性,同时分析了荷载大小、土层性状对响应结果的影响,得出了一些有意义的结论。研究结果可为路面施工设计及路基动力响应分析提供参考。 相似文献
13.
The axisymmetric elastic response of circular footings and anchor plates in a linearly non-homogeneous elastic soil is analysed. It is assumed that footings/anchors are flexible and subjected to axisymmetric vertical loads. The response of the footing/anchor is modelled by using the classical Poisson–Kirchhoff thin plate theory. A variational technique is used to analyse the interaction problem. A representation for the contact stress is established by using a fundamental solution corresponding to a unit vertical pressure acting over an annular region in the interior of the non-homogeneous soil. The fundamental solution can be derived by using rigorous analytical procedures. The influence of the footing flexibility and the degree of soil non-homogeneity on the displacements, bending moments and contact stresses of a surface footing is examined over a wide range of governing parameters. In the case of anchor plates the influence of depth of embedment, degree of soil non-homogeneity and anchor flexibility on the anchor displacement is investigated. 相似文献
14.
Euclides Mesquita Marco Adolph Edson Rodrigues Carvalho Edivaldo Romanini 《国际地质力学数值与分析法杂志》2009,33(18):1933-1952
In this article a numerical solution for a three‐dimensional isotropic, viscoelastic half‐space subjected to concentrated surface stress loadings is synthesized with the aid of the Radon and Fourier integral transforms. Dynamic displacement and stress fields are computed for points at the surface and inside the domain. The analysis is performed in the frequency domain. Viscoelastic effects are incorporated by means of the elastic–viscoelastic correspondence principle. The equations of motion are solved in the Radon–Fourier transformed domain. Inverse transformations to the physical domain are accomplished numerically. The scheme used to perform the numerical inverse transformations is addressed. The solution is validated by comparison with results available in the literature. A set of original dynamic displacement and stress solutions for points within the half‐space is presented. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
15.
This paper presents a mechanical analogue which models the response of a rigid circular footing on an ideal elastoplastic half-space to transient loads. In the rational analysis of pile-driving dynamics, the response of soil at the base of a pile is often approximated by a footing on a semi-infinite half-space. Most existing base models employ the well-known Lysmer analogue to model the elastic response of the soil at the pile base, and account for the inelastic soil behaviour through the inclusion of a plastic slider with a slip load equal to the ultimate failure load of the footing. The improved model provides a force response which is significantly closer to the ideal response than existing models. The paper commences with a review of analytical solutions for the dynamic response of a rigid circular footing on an elastic half-space. Existing mechanical analogs for the system are reviewed, and an automatic matching process proposed which improves the accuracy of the analogs under transient loading. The inelastic response is then studied using the finite element method, and the mechanical analogs are modified to allow representation of the observed inelastic behaviour. Examples are presented illustrating close agreement between the proposed models and finite element analyses for a range of Poisson's ratio. The improved models have direct application for one-dimensional models of pile driving, particularly in the back-analysis of data from dynamic testing of piles. They are also applicable to studies of dynamic compaction. 相似文献
16.
A single pile embedded in a layered poroelastic half‐space subjected to a harmonic lateral load is investigated in this study. Based on Biot's theory, the frequency domain fundamental solution for a horizontal circular patch load applied in the layered poroelastic half‐space is derived via the transmission and reflection matrices method. Utilizing Muki and Sternberg's method, the second kind of Fredholm integral equation describing the dynamic interaction between the layered half‐space and the pile subjected to a top harmonic lateral load is constructed. The proposed methodology is validated by comparing results of this paper with some existing results. Numerical results show that for a two‐layered half‐space, the thickness of the upper softer layer has pronounced influences on the dynamic response of the pile and the half‐space. For a three‐layered half‐space, the presence of a softer middle layer in the layered half‐space will enhance the compliance for the pile significantly, while a stiffer middle layer will diminish the dynamic compliance of the pile considerably. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
17.
Elastic lateral dynamic impedance functions are defined as the ratio of the lateral dynamic force/moment to the corresponding lateral displacement/rotation at the top ending of a foundation at very small strains. Elastic lateral dynamic impedance functions have a defining influence on the natural frequencies of offshore wind turbines supported on cylindrical shell type foundations, such as suction caissons, bucket foundations, and monopiles. This paper considers the coupled horizontal and rocking vibration of a cylindrical shell type foundation embedded in a fully saturated poroelastic seabed in contact with a seawater half‐space. The formulation of the coupled seawater–shell–seabed vibration problem is simplified by treating the shell as a rigid one. The rigid shell vibration problem is approached by the integral equation method using ring‐load Green's functions for a layered seawater‐seabed half‐space. By considering the boundary conditions at the shell–soil interface, the shell vibration problem is reduced to Fredholm integral equations. Through an analysis of the corresponding Cauchy singular equations, the intrinsic singular characteristics of the problem are rendered explicit. With the singularities incorporated into the solution representation, an effective numerical method involving Gauss–Chebyshev method is developed for the governing Fredholm equations. Selected numerical results for the dynamic contact load distributions, displacements of the shell, and lateral dynamic impedance functions are examined for different shell length–radius ratio, poroelastic materials, and frequencies of excitation. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
Morteza Eskandari‐Ghadi Azizollah Ardeshir‐Behrestaghi Ronald Y. S. Pak Mostafa Karimi Masoud Momeni‐Badeleh 《国际地质力学数值与分析法杂志》2013,37(14):2301-2320
An analytical investigation of a half‐space containing transversely isotropic material under forced vertical and horizontal displacements applied on a rectangular rigid foundation is presented in this paper. With the goal of a rigorous solution to the shape‐ and rigidity‐ induced singular mixed boundary value problem, the formulation employs scalar potential representation, the Fourier expansion and the Hankel integral transforms method to obtain the surface arbitrary point‐load solution in cylindrical coordinate system. The obtained Green's functions are rewritten in rectangular coordinate system, allowing the response of the half‐space because of an arbitrary distributed load on a rectangular surface area be given in terms of a double integral. The numerical evaluations of stresses are done with the use of an element, which is singular at the edge and the corner of the rectangle. Upon the imposition of the rigidity displacement boundary condition for a rigid foundation and the use of a set of two‐dimensional adaptive‐gradient elements, which can capture the singular behavior in the contact stress effectively, a set of new numerical results are presented to illustrate the effect of transverse isotropy on the foundation response. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
19.
交通荷载作用下Kelvin地基上不平整路面的动力响应分析 总被引：4，自引：2，他引：2
为了评价不平整路面在交通荷载作用下的动态响应,从路面几何不平整出发,假设路面不平整服从正弦函数曲线,并把1/4车身结构简化为2个自由度振动体系,得到了不平整路面上的动荷载表达式。又将此荷载模式看成是作用在Kelvin地基上无限大路面板表面的移动矩形荷载,采用双重Fourier变换方法得到了不平整无限大路面板竖向位移的积分形式解,此解析解可以退化为静荷载作用下的经典解答。并利用快速傅立叶变换(FFT)方法得到了数值计算结果。分析了荷载速度,路面不平整波长、不平整幅值以及地基阻尼和地基刚度对板的动力响应的影响。结果表明,板竖向位移的分布受荷载移动速度的影响;位移幅值随着路面不平整波长和荷载速度的变化出现2个峰值;路面不平整使得位移峰值出现滞后现象,且不平整波长越小或不平整幅值越大,滞后现象越明显。 相似文献
20.
Bearing Capacity of Strip Footings Near Slopes 总被引：2，自引：1，他引：1
In the last decades a great attention was given by many authors to the evaluation of the static and seismic bearing capacity
of footings near slopes. In this paper a model has been developed based on the limit equilibrium method, considering a circular
surface propagates towards the slope until the sloping ground is reached. The bearing capacity is investigated considering
either the distance of the footing from the edge of the slope and/or the effect of the footing embedment. A validation of
the proposed model was made by a comparison with solutions taken from literature regarding the evaluation of the bearing capacity
for a footing adjacent to a slope and for an inclined load. The loading conditions consist in vertical and horizontal stress
on the footing and on the soil below the footing. Both the inertial and kinematic effects of the seismic loading have been
analyzed, and a simple equation has been derived for the evaluation of the seismic bearing capacity. The static and seismic
bearing capacity has been investigated as a function of the soil friction angle, of the seismic coefficient, of the sloping
ground. Finally, the influence of the distance of the footing from the edge of the slope was taken into consideration in the
evaluation of the bearing capacity, and a threshold distance at which the reduction of the bearing capacity due to the sloping
ground vanishes has been defined. 相似文献